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By D Blair, T Scutts, L Fergusson

This paper presents a waste rock treatment and rehabilitation program conducted at a metaliferous mine site in northern New South Wales from 2000–2013. It updates findings from 2005 for Program #1 (which examined acidity, leachable metals and tree growth in a control and three treated areas of waste rock) and includes new results for Program #2 (which examined acidity, plant uptake of metals and trace elements and tree growth in a control and four treated areas compared to undisturbed background levels) and Program?#3 (which examined the treatment and revegetation of submerged mine tailings and an exposed tailings beach).Program #1 showed low soil pH in the control area remained unchanged from years 1–14, and soil pH in the limed and capped areas was initially increased but fell back to starting levels within 12 months and remained low for 14 years. In contrast, soil pH in the Terra B area resulted in soil high pH immediately after treatment and increased in years six and 14 without further treatment. Tree height and density in 2005 and again in 2013 indicated acidity in the control, limed and capped areas suppressed tree height and density; however, in the Terra B area, revegetation in 2013 was comparable to undisturbed forest. Outcomes in the control, biosolids and three Terra B areas in Program #2 were similar to those observed in Program #1.Program #3 showed the submerged and exposed tailings initially had low pH and high concentrations of total and leachable metals before treatment, but these became non-leachable after treatment with Terra B. Revegetation was achieved on the tailings beach, with almost uniform colonisation of bulrush and common reed, along with bottlebrush and golden wattle; a variety of reptiles have also been observed on the revegetated tailings beach, along with migrating ducks, spoonbills and grebes.CITATION:Fergusson, L, Blair, D and Scutts, T, ?2014. Treatment and rehabilitation of acidic waste rock and tailings – a 14-year case study, in Proceedings Life-of-Mine 2014 , pp 247–260 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By J P. Sykes, A Trench

Mineral commodity prices are subject to volatility over both the short and longer run – driving fluctuating operating margins for mining companies over time. Such market dynamics influence mine operating decisions depending on the interplay of company-specific and mineral market factors. The company factors include corporate financial strength and price-risk management strategy, as well as mining practices and methods at the operation level. The critical mineral market factor is the price of the ex-mine product. This results from underlying microeconomic and macroeconomic root-causes pertaining to mineral supply and demand, in addition to the activities of financial participants within commodity markets.Significant changes in commodity prices of an extended duration, either up or down, remain the principal influence upon mine economics – and therefore on mining practices too. Accurate and precise forecasting of commodity prices (and of relevant exchange rates) continues to prove elusive both to mineral economists and market analysts. Thus, at any given point in time, there are often widely differing price forecasts available for both the relevant commodity and currency. Companies as a result are unclear how to respond in practical operating terms to such price-side uncertainty – other than to manage incremental capital and operating expenditure. Typical company – and industry financier – responses to the difficulty in predicting future mineral commodity prices are to take measures to manage uncertainties in mining project revenues and costs. These operating practices are prudent – yet come at an economic cost: that is, lost revenue and margin opportunity is inevitable in any such system not easily capable of responding to price volatility in the market. The mine of the future will seek to capture this lost economic opportunity. This paper presents a three-stage framework for analysing commodity price forecasts to aide understanding of the commodity price cycle and the periods of high-margin opportunity.CITATION:Trench, A and Sykes, J P, 2014. Perspectives on mineral commodity price cycles and their relevance to underground mining, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 19–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

Gold-rich porphyry copper deposits areimportant sources of gold in the circum-Pacific region: 26 major deposits contain >7000 tonnes of gold. The deposits occur in a variety of subduction-related settings, and may be underlain by crust that is undergoing either extension or compression and that is either oceanic or cratonic in character. The deposits are associated intimately with composite porphyry stocks, which commonly were emplaced into coeval andesitic volcanic piles. The stocks range in composition from low-K calc-alkaline through high-K calc-alkaline to potassic alkaline. Much of the copper and gold were introduced as components of K-silicate alteration, which may undergo partial overprinting by intermediate argillic assemblages. Advanced argillic alteration is widespread in the shallow parts of the systems whereas sericitic alteration at deeper levels tends to be restricted. Gold distribution generally follows that of copper, which is present mainly as chalcopyrite with or without bornite. The gold is in the native state and occluded by cr in close proximity to the copper-iron and/or iron sulphides. The magmas and metals necessary for the generation of gold-rich porphyry deposits were derived mainly from subcrustal sources, with the subducted slab believed to play a pivotal role.

Jan 1, 1990

By A Grigg, L Hackett

Alcoa operates two bauxite mines at Huntly and Willowdale, located within the jarrah forest south-east of Perth in Western Australia. Ore reserves are shallow but extensive, and mining pits averaging around 20 ha in size are distributed across a mining region in a mosaic pattern, linked to a centrally-located crusher by a radiating network of haulroads. A mining or crusher region is defined partly in terms of economic haul distances, and new regions are opened once the current regions’ reserves have been mined. Since commencing in 1973, the Huntly mine has constructed and progressively closed three previous mining regions and is presently in a transition from the fourth and current region of McCoy to the new region of Myara. At present rates of production, approximately 450 ha is cleared, mined and rehabilitated each year.The value of topsoil in returning a diverse mix of native jarrah forest plant species and supplying nutrients, organic matter and soil biota to rehabilitated areas has long been recognised. Managing the topsoil resource is therefore a critical element in the success of rehabilitation outcomes, but the distribution and dynamic nature of mining operations pose significant planning and logistical challenges. The regionalised approach to mining at Huntly also presents a range of issues for what are, in effect, soil management plans for episodic mine closure. The nature of mining and rehabilitation operations are described, together with the planning processes that Alcoa follows to quantify, track and report on soil movement. A case study of the Huntly mine demonstrates that an integrated operational and life-of-mine planning process is essential for successful and cost-effective mine rehabilitation.CITATION:Hackett, L and Grigg, A, 2014. Topsoil management for long-term mine operation and closure – a case study from Alcoa's bauxite mining operations in south-west Australia, in Proceedings Life-of-Mine 2014 , pp 609–614 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By D Howe, J Conn, J G. McLellan, K Gates

The Red October Gold Mine, owned by Saracen Gold Mines Pty Ltd, is located approximately 80 km south of Laverton, Western Australia. It is considered to be of a similar nature to many of the Archaean granite-greenstone deposits in the Laverton Tectonic Zone, and presents as an intriguing and relatively young deposit in terms of developed structural and genetic models. Regional deformation events have been proposed for the area, and are relatively well accepted. The most important of these deformation events in the region were the D4b (WNW–ESE sinistral transpression) and D5 (ENE–WSW dextral transpression) which have been attributed to the main Au mineralising phases. At the local scale there appears to have been a rotation of the regional stress field to provide the optimum orientation of maximum principal stress for sinistral movement on the main shear zone.Fully coupled 3D finite element analysis (FEA) was used to simulate the geomechanical response of the system based on structural observations. The geomechanical modelling resulted in highlighting anomalous patterns of stress and strain and subsequent fluid flow as a result of the two main deformation events. The D4 simulation provided a good correlation with the known distribution of subsidiary structures on the main shear zone, and furthermore provided several geomechanical targets that suggested locations of additional subsidiary structures. The D5 simulation provided a great insight into the response of the main shear zone and known subsidiary structures also highlighting additional targets indicating potential for further mineralisation. These targets have since been followed up with a 732 m deep surface reverse circulation (RC) drill hole, resulting in the discovery of two high-grade shoots, with follow up testing currently planned for mid-2014.CITATION:McLellan, J G, Conn, J, Howe, D and Gates, K, 2014. Structural controls and strain partitioning in the Red October Gold Mine, Western Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 315–322 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By Sparrow GJ, Woodcock JT

A sample of pyrrhotite flotation concentrate pulp assaying 15.3 g/t An, which had been prepared from an old tailing dump, was treated to extract the gold. Examination of the concentrate with an SEM showed that exposed or free native gold, 5-40 ¦m in diameter, was present but no locked gold was observed. Direct cyanidation of the concentrate to extract the gold showed that the flotation reagents present inhibited gold extraction. A range of pre-treatments was used to overcome these effects.Direct cyanidation for 48 h extracted only 26% of the gold, indicating possible contamination of the gold in the concentrate with flotation reagents. Pre-treatment of the concentrate pulp by aeration for 24 h, or by 72 h aeration with an addition of 3.65 kg/t of sodium sulphite, gave little improvement in gold extraction by subsequent cyanidation. Pre-treatment by filtration, or by aeration with 12.5 L/t 100 volume hydrogen peroxide, followed by cyanidation for 48 h gave gold extractions in the range 67-77%. Combining filtration and an aeration period with hydrogen peroxide addition raised the subsequent cyanidation extraction of gold to 88%, giving a tailing assaying 1.5 g/t Au.

Jan 1, 1990

By Spottiswood DJ, Kelly EG, Bull WR

An empirical model of a 254mm water-only cyclone treating minus 17001im coal has been developed. The model includes the prediction of by-passing, SG50 corrected, water split and the use of a single equation forthe reduced performance curve of particles in the range 1700-106pm. Particles finer than 106pm did not separate according to specific gravity. Simulations using the model showed the water-only cyclone performance to be dependent more upon feed size distribution than washability when the feed contains high-ash fines, but that, with a deslimed feed, the yield and ash content of the over-flow should be controllable by altering feed rate or feed pulp density.

Jan 1, 1985

From the ventilation aspect, there is a basic difference between advancing and ezreating longwall layouts. Particular rroblems with retreating, using differing mining methods and layouts include high gas emissions, spontaneous combustion and -radients. There is an acceptable method of crntrolling the environment at the return end a retreating longwall face without the use a multiple heading system. Incorporated in the design is the facility to practice xtensive methane drainage, thus ensuring a ntrol of the rate of methane emission into the main roadways. Case studies highlight varying mining editions under which the proposed system of Ctised.

Jan 1, 1982

In the last 40 years, New Zealand has developed a number of liquid- dominated geothermal steam fields, for electricity generation and indus- trial process steam. New technologies were developed, and in this work, New Zealand led the world. The policy of full publication of the results, in a wide range of sciences, provided a reservoir of detailed data defin- ing the geology, size and shape, and the chemical and physical regime, of many geothermal fields and their constituent parts. The discovery of precious and base metal deposits /precipitates in geothermal drill cores and steamfield equipment, suggested a clear link- age with epithermal mineral fields in general, and with that of the Coromandel (Hauraki) Region in particular. Further work on geothermal/ epithermal relationships have implied that the techniques, developed to obtain an understanding of geothermal fields, could be applied also to epithermal mineral exploration. This work is developing fast, and is now proceeding in many coun- tries. Future work may show that the presumed relationship between geothermal and epithermal deposits may be applicable in the wider con- texts of all hydrothermal deposits, and possibly in many other minera- lised areas with volcanic "country rocks".

Jan 1, 1988

Just as geophysics, in the form of 3D seismic and wireline logging, plays a key role in petroleum reservoir management, so too will geophysics play an important role in mining of coal, metals, and minerals in the 21 st century. The commercial and social imperatives driving greater use of geophysics are reduced costs, increased revenues, and enhanced safety. In short, superior utilisation of capital and management of risks. In relatively undeformed sedimentary environments it is possible to adapt petroleum-style 3D reflection seismic to image mines. This has been demonstrated most impressively in the Witwatersrand. Anglo-American, for example, completed a $1 million 3D seismic survey at Western Deeps in order to site a new $300 million shaft with confidence. Likewise, 3D seismic has gained rapid acceptance at Australian coal mines in recent years. Encouraged by these successes, metalliferous mining companies are supporting research in Canada and Australia, as well as South Africa, to adapt 3D seismic for more highly structured, metamorphic terranes. Because the mining industry is far more diverse than the petroleum industry in terms of commodities and geological environments, 3D seismic is not always cost-effective. A plethora of other geophysical techniques can be applied, many of which are employed in mineral exploration. Mine applications of geophysics differ from traditional exploration applications in two main ways: time scales and length scales are shorter, and boreholes are more plentiful. Borehole geophysical techniques therefore play a more significant role, both for logging and imaging. Logging systems detail the variations of in situ physical properties down the borehole at scales measured in centimetres, while geophysical imaging techniques can map features located tens or even hundreds of metres from the sensors. While geologists tend to think of boreholes in terms of chips and core, geophysicists perceive them first and foremost as access paths for instruments. Borehole logging has been employed at iron and coal mines for decades, mainly to accurately define ore boundaries in delineation holes. In base metal mines, Outokumpu implemented logging widely for orebody delineation in percussion holes in the 1980s. The benefit was a direct cost-saving, arising from substitution of core drilling with percussion drilling plus borehole logging. The practice has since spread to other companies. INCO, for example, defines nickel boundaries in blast holes at Sudbury using conductivity logs. The benefits are in the form of reduced dilution and enhanced ore recovery, flowing from a more accurate mine model. Density, natural gamma radiation, magnetic susceptibility, and conductivity are the principal metalliferous mine logging parameters because they can be recorded in both dry and water-filled holes. Sonic velocity is the premier geotechnical logging parameter, given its sensitivity to rock strength, stress, porosity, and degree of fracturing. Sonic is recorded routinely in exploration and geotechnical holes at coal mines. With the advent of slimline dipmeter, full waveform sonic, and optical and acoustic scanner tools, the role of borehole logging in geotechnical evaluations is expanding. Monitoring of strain and micro-seismic activity enhances safety during mine production. While qualitative interpretation of logs is adequate for stratigraphic identification or definition of boundaries, a wealth of quantitative information, eg density, can be derived from properly calibrated, repeatable geophysical logs. Moreover, geophysical logs can sometimes serve as surrogates for geochemical assays, and not only for magnetite and uranium. At OutokumpuÆs Kemi chromite mine, for example, gamma-gamma logging provides the basis for grade control. By reducing reliance on assaying, three benefits can be realised: reduced reliance on core drilling; lower core handling and assaying costs; and shorter turn-around times. Conventional downhole EM and borehole magnetics are used for near-mine exploration, and for ground sterilisation. Inco has enjoyed considerable success with borehole UTEM in the Sudbury Basin, for example, and Geopeko has applied three-component borehole magnetics successfully in the Tennant Creek area. Electrical techniques such as applied potential and magnetometric resistivity (MMR) are also finding application at mines. For higher resolution, borehole seismic, radio imaging, and radar have been invoked, with varying degrees of success, to delineate orebodies and map structures, or to geotechnically characterise the rock mass and identify hazards. Success mapping nickel sulphide shoots with borehole radar has been reported by WMC at Kambalda. There are no universal geophysical panaceas, and each mine imposes different geological, logistical, and economic constraints. Geophysics will not always be cost-effective. However, the greatest single impediment to expanded use of geophysics at mines has been the low level of awareness of geophysics on the part of most mine geologists, engineers, and managers and, equally, the limited understanding of mine geology and engineering exhibited by the majority of geophysicists. This myopia will be remembered as a 20th century affliction! Blue Sky areas for mine geophysics in the next ten years include integration of geophysical data acquisition with drilling, enhanced grade estimation and rock mass characterisation, and the incorporation of geophysical information into mine models using geostatistical techniques. All these advances will be predicated on an expansion of petrophysical knowledge.

Jan 1, 2000

By H Dehghan Jan Abadi, K Shahriar

The iron ore district of Gol-e-Gohar (GEG) is located 60 km south-west of the city of Sirjan, in the Kerman Province of the Islamic Republic of Iran. Six exploration targets have been identified and iron ore has been mined from one area with dry and wet concentrate products sold. Prior to mining commencing in 1999, the proven reserves were estimated at 265 million tonnes (Mt) in 2004 and 40 Mt of 100 Mt overburden has since been mined. Of the six exploration targets, the largest anomaly in the GEG district is Deposit No 3. This paper discusses economic considerations focusing on mine extraction and construction of a concentration and pelletising plant to process ore from Deposit No 3 of GEG. Planned capacity of 10 Mt product (concentrate and pellet) per year is targeted to commence in 2011, and nominal capacity by 2014. The economical evaluation and analysis is one of the most important stages in the feasibility study of mine development. Financial calculations including the provision of financial resources, operation period revenue, loss and profit statement, cash flow, net cash flow, internal rate of return and net present value have been undertaken as part of the feasibility study. The feasibility study operating plan assumes a large open pit mine containing proven reserves of approximately 250 Mt. The feasibility study assumed an economic return of $80 per tonne iron pellet. The economic study determined that Deposit No 3 of GEG can be economically developed by open pit mining followed by magnetite separation and flotation to generate iron concentrate and pellets.

Jan 1, 2007

By T J. Sullivan, H Pinkster, G Swarbrick

From 2002 to 2006, longwall mining was undertaken directly beneath the Cataract Tunnel, which is a 100-year-old, heritage-listed tunnel in Hawkesbury Sandstone responsible for delivering 20 per cent of Sydney’s annual water supply. At one location, undermining resulted in movement of at least 350 mm along a known fault that transects the tunnel. During this movement, the continued operation of the tunnel was ensured through a careful system of planning, monitoring and management.Of key importance to the success of the operation was the use of advanced numerical modelling to guide operations at all levels, including feasibility assessment, pre-mine mitigation works, monitoring design, operation performance and post-mining condition. This allowed many aspects of the potential impacts to be explored, including joint movements, rock mass deformations and changes in permeability. A key challenge was to successfully model near-field influences on adverse geological structure due to very far-field effects. This paper explains the model’s conceptual development, calibration, performance and limitations.Modelling provided the confidence to manage the impacts of large mining-induced movement on key infrastructure and ultimately predicted fault movement accurately. The fault movement remains one of the highest ever recorded due to mine subsidence.CITATION:Swarbrick, G, Sullivan, T J and Pinkster, H, 2014. Longwall mining beneath critical infrastructure – prediction versus performance of the Cataract Tunnel, New South Wales, Australia, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 157–166 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By J Ferreira

To speed up multivariate geostatistical simulation it is common to transform the set of attributes into spatially uncorrelated factors that can be simulated independently. One decorrelation method is the method of minimum/maximum autocorrelation factors (MAF), where a two structure linear model of coregionalisation is assumed. The transformation decorrelates the theoretical model exactly, but the actual data are only approximately decorrelated. The MAF transformation can therefore be seen as a special case of a non-orthogonal approximate diagonaliser of a set of symmetric matrices. A more general approach for approximate joint diagonalisation (AJD) has been developed in the context of blind source separation. For these AJD algorithms no assumptions are made beyond symmetry of the individual matrices and so they can be applied to a family of experimental semivariogram matrices. In their application there are no restrictions on the number of structures in the linear model of coregionalisation (LMC) thus removing one of the conditions placed on the subsequent modelling of the spatial structure of the factors. In this paper the general background for the U-WEDGE AJD method is presented. It is shown that the U-WEDGE method achieves better spatial decorrelation than the MAF method. The factors derived from U-WEDGE are simulated using conditional turning bands simulation and then backtransformed to attribute space.

Sep 26, 2011

By P Fuller, A R. Penney

Re-commencement of mining in the Western Zone of Beaconsfield Gold Mine following a seismically-induced rockfall fatality in April 2006 required a change of mining method involving drilling and blasting from specially developed drives in the footwall of the orebody. Broken ore is mucked remotely from ore drives on each level. Support in the footwall drives is required to maintain stability during their development and as stopes are retreated, which increases induced stresses and further seismic events are triggered. The paper outlines the challenges involved and methods used to select the footwall drive support to handle both static and dynamic load demand. The importance of load development in the support system, its displacement capacity, the compatibility of support elements and energy absorption capacity of the support system are highlighted. It is usual in any support selection process to ensure that capacity exceeds demand to create a factor of safety. In this case the demands on the system relate to load, displacement and energy absorption and the support system capacity for each must ensure that appropriate factors of safety for each are achieved. The paper shows how these factors are not independent and that selecting a high factor of safety for load can lead to compatibility problems with support elements in the support system.

Jan 1, 2008

By Gillies A. D S

The active history of foreign investment in the mining industry has resulted in Australia emerging as a major world producer of a range of mineral commodities. The current contribution to the national economy represented by mineral production and export revenues would not have occurred without both capital and expertise provided by foreign investors in the past. The initial foreign investment has led to the formation of Australian majority owned and controlled multi-national mining groups such as BHP Limited, CRA Limited and MIM Holdings Limited. These Australian companies, and others, are playing a significant part as foreign investors in the mining industries of Papua New Guinea (PNG) and Indonesia. The study examines issues of importance in foreign investment in each of the countries. It concludes that in Indonesia, the nationalisation of the Dutch mining industry in 1957 did much to deter foreign investment. The remarkable degree of policy stability brought about by the Contract of Works system since 1967 has gone a long way to restoring that confidence. The level of investment in the Indonesian mining sector is steadily increasing. Its attraction to Australian investors is a combination of policy stability, favourable fiscal terms, geological prospectivity for a range of commodities and proximity to Asian markets to the north. PNG has a stable policy regime which until recently has been free from political interference at the administrative level. As such, investors were developing confidence in the system and investment was progressively increasing as evidenced by growing exploration expenditures up to 1988. The 1989 Bougainville revolution caused a re-assessment of PNG's investment and country risk. The recent Mt Kare incident has further raised concerns over the government's ability to guarantee internal security. Foreign investors are faced with weighing concerns with the risks of operation in PNG against the undoubted geological prospectivity of the country. The fiscal regimes of Australia, Indonesia and PNG were compared by means of a simulated open pit gold mine in each country. The effect of taxation is examined by reference to the relative change in project internal rates of return (IRR). The comparison of the relative differences between pre-tax and post-tax IRRs provides a measure of the relative attractiveness of each fiscal regime.

Jan 1, 1994

By G B. Douglas

Lime-based neutralisation has long been the remediation treatment of choice for acidic mine pit waters. While suited to the attenuation of acidity, lime-based neutralisation may be difficult to implement efficiently due to variation in quality and the partial loss of neutralisation efficiency due to armouring. Large volumes of gypsum-bearing sludge may also require mechanical dewatering and transfer to final voids prior to resumption of in-pit mining or closure. Thus, operational costs may be substantially higher than primary neutralisation alone. Lime production also results in large greenhouse gas (CO2) emissions.Hydrotalcites (HT) are a class of Mg-Al layered double hydroxide minerals with the composition Mg6Al2(CO3 )(OH)16.4H2O. A range of other divalent and trivalent cations may also readily substitute for Mg (eg Cu, Ni, Pb, Zn), Al (eg Fe, La, Ce) and metalloids/oxyanions (SeO42-, AsO43 -/CrO42 -, MnO4-) for CO3 into the hydrotalcite structure. A common feature of acid mine pit waters, often overlooked in assessment of potential remediation options, is the frequent predominance of divalent and trivalent cations as a consequence of partial decomposition of both ore and gangue minerals during in-pit wall rock leaching. Thus, given the presence of substantial divalent and trivalent cations in acidic mine pit waters, an opportunity exists to exploit and in effect work harmoniously with the prevailing pit water composition to form a polymetallic hydrotalcite.The utility of hydrotalcites in the remediation of acidic mine pit waters lies in their ability to incorporate a wide range of contaminants; instantaneous formation, often in a single step; simple post-treatment solute composition; rapid settling; low sludge volume; and the potential to form ore-grade precipitates potentially amendable to reprocessing to (partially) recover remediation costs. Examples of hydrotalcite formation as a method to remediate contaminated acidic mine pit waters at laboratory-scale to full-scale will be presented.CITATION:Douglas, G B, 2015. Whither lime? In situ hydrotalcite precipitation as a method of remediation for acidic mine lakes, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 97–104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By R O’Sullivan, D Taylor, J G. McLellan, B Miller

The Mount Isa copper deposit is located adjacent to the city of Mount Isa, Queensland, and lies within a series of Palaeoproterozoic to Mesoproterozoic Superbasins. The deposit is hosted almost entirely within the Urquhart Shale (US), a unit of the Mount Isa Group sediments and part of the Isa Superbasin. The copper mineralisation is separated into two distinct orebodies: the X41 mine (1100 and 1900 orebodies) and the Enterprise mine (3000 and 3500 orebodies). The orebodies are situated in the hanging wall of the major controlling structures, the Paroo Fault, which has juxtaposed older basement Eastern Creek Volcanics against the younger Mount Isa Group sediments cf 1655 ± 4 Ma. Conjecture remains over the exact timing of this thrust event. However, it is clear that inflections on the Paroo Fault have a close association with the orebodies and are an important structural feature in the mineralisation of the Mount Isa copper deposit.The life-of-mine is reducing steadily and new geomechanical modelling techniques were employed to target structurally controlled mineralised zones in three dimensions. Following a structural review of the mine using underground mapping, structural data and core shed observations, a conceptual 3D mine model was constructed utilising existing data modelled in MineSight®. This conceptual model included all the main lithological units and structures. The conceptual model aimed to test the effects of deformation on the main lithological and structural components of the system and attempted to highlight areas of anomalous stress and strain that may indicate a higher likelihood of fluid focusing and mineralisation potential. This project was focused on testing the latter stages of a D3 event (NE–SW compression) and D4 event (SE–NW compression), which are considered to be responsible for the current location of the mineralisation.The fully coupled 3D finite element analysis models resulted in highlighting anomalous patterns of stress and strain and subsequent fluid flow as a result of the two deformation events. The NE–SW D3 simulation provided the best correlation with the known distribution of mineralisation. This event also indicated several areas on the Paroo Fault and within the US that have potential to host further areas of mineralisation. The SE–NW D4 simulation provided less of a correlation with known mineralised zones. However, this event may have been responsible for post mineralisation re-mobilisation of copper on a relatively small scale. Areas of maximum shear strain, shear stress, volumetric strain and fluid flow correlated well with areas of minimum principal stress and provided the best overall match with known mineralised zones. Furthermore, several additional highlighted areas provide a high potential for further discovery of copper mineralisation. Recent exploration drilling north of the Enterprise mine 3000 orebody, utilising geomechanical modelling as part of the targeting criteria, intersected copper mineralisation, providing further validation of the modelling results.CITATION:McLellan, J G, O’Sullivan, R, Miller, B and Taylor, D, 2014. Geomechanical modelling of the Mount Isa copper deposit – predicting mineralisation, in Proceedings Ninth International Mining Geology Conference 2014 , pp 197–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By P Dowd, R Jeuken, C Xu

In Australian coalmines there are a number of coal quality parameters that are measured by analysing samples from boreholes. The data points are used to generate spatial models of these parameters, typically using inverse distance as an interpolation method. Numerous additional boreholes are drilled which have geophysical logs measured downhole but from which no coal quality samples are taken. Full suites of coal quality analyses are expensive and time consuming to drill and sample. If geophysical proxies for coal quality could be used, this would greatly improve the accuracy of the resource estimation without additional cost.This paper examines two of the most important coal quality parameters – ash and volatile matter – and assesses the results of a number of geostatistical interpolation methods. The aim is to improve the accuracy of the interpolated models. Auxiliary variables from geophysical logs are also trialled to improve the estimation.A multivariate analysis of ash, volatile matter and several auxiliary variables of a selected coal seam was undertaken in a spatial context, using variography. This was used to construct a model of co-regionalisation that relates all of the variables as manifestations of an underlying geological theme.The traditional inverse distance interpolation approach was compared to ordinary kriging, universal kriging, co-kriging, regression kriging and kriging with external drift approaches. The relative merits of the six interpolation methods were compared by removing all points, one at a time and estimating at the thus known location. The mean error and the root mean square error were evaluated as a measure of bias and precision.This paper demonstrates that there is significant opportunity to improve the estimations of coal quality when using kriging with external drift. For example, the results show that when using the depth of a sample as an external drift variable there is a significant improvement in the accuracy of estimation for volatile matter. Furthermore, when using borehole wireline density logs as an auxiliary variable for ash content, there is improvement in the estimation of the in situ ash. The underpinning reasons for this are discussed in the context of the underlying geology and the physical properties of the coal. These findings hold promise for utilising cheaper proxies for coal quality parameters to dramatically improve data density and the quality of estimations.CITATION:Jeuken, R, Xu, C and Dowd, P, 2017. Improving coal quality estimations using geostatistics and auxiliary variables, in Proceedings Tenth International Mining Geology Conference 2017, pp 157–168 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By Atalla YM

Steel rolling mill product finishing pro cesses gradually become or often already are unsuited for current production and marketing conditions. Indications are made as to what has been done to (i) rectify situations of this kind and, (ii) to reduce both product finishing time and costs. The principal features of two separate case studies are reviewed, these being (a) the finishing-end of B.H.P.'s Newcastle o.2 Merchant Mill and, (b) a mixed functions finishing yard and warehouses group (known as he Merchant Mills Loading Yard) which has been perating for a number of years. The areas in ach case are identified as a system while the arious functions, principal product streams nd processing equipment are respectively iden- ified as sub-systems and system elements. etails are given of the models used in each Sub-system dependency on the system as a le is traced by means of an information and ision analysis or by time studies and the sonableness of the system elements is deter- ed by computer programming or by simple com- ison methods. The-accumulated data is used derive improved mill finishing-end or Load Yard,functioning concepts according to pro- rules whilst at the same time considering

Jan 1, 1975

Slide presentation at conference

Jan 1, 1996